At this point it would be useful, with regard to the present invention, to discuss related art. A search of this art has noted the following patent references. A careful review of these patents, readily distinguishes present invention from any of this earlier art.
U.S. Pat. No. 5,608,554--This reference pertains only to a 2D-Display medium and uses non-coherent light sources. It does not employ Holography or 3D PA0 U.S. Pat. No. 5,122,882 This reference pertains to 2D-animated display medium (no 3D or holography involved). In addition it utilizes a white light source and a simulated display. PA0 U.S. Pat. No. 5,122,890 This reference is similar to the above reference U.S. Pat. No. 5,122,882. It represents a 2D-animated display (no 3D or holography involved)and utilizes a white light source and a simulated display. PA0 U.S. Pat. No. 5,517,278 This patent represents a 2D display device for video camera viewfinder and is not used for holography. It uses a non-coherent light source. PA0 U.S. Pat. No. 5,440,428 This reference is totally unrelated to the present invention. It is for an improved automotive (heads-up display, is not a holographic 3D display medium. It represents a mirror system (can utilize a permanent holographic narrow band reflecting mirror) and no PLZTs used. PA0 U.S. Pat. No. 5,589,980 This patent represents a 2D or simulated 3D display (not holographic). It uses layered images in a projection system to simulate 3D and is completely different from the present application. PA0 U.S. Pat. No. 5,552,840 This reference utilizes stereoscopic vision to simulate a 3D image (uses parallax). No holography used and it uses S and P polarized light to provide stereoscopic images and eyeglasses that separate the light for left and right eye viewing. It is completely different from the present invention. PA0 IBM Technical Disclosure Bulletin vol28 no.6 November 1985 Uses PLZTs for color filters and not a holographic display medium. This is not a display system. PA0 Japanese Patent No.JP60006922A This patent employs Optical control element to make high-speed optical shutters and has nothing to do with a holographic display. PA0 Japanese Patent No. JP59018932A Represents an Optical deflecting device and has nothing to with holographic displays.
As noted in the above referenced copending patent application, Ser. No. 09/182,075, filed on Oct. 29, 1998, describes a PLZT inorganic material. This PLZT material serves as the basis of the present application and is a Lanthanum enhanced lead zirconate titanate material. It is piezoelectric/optic ceramic material. It would now be helpful to the understanding of the present invention to describe the composition and nature of this PLZT ceramic material.
PLZT can be prepared in the following two ways. In one case a mixed oxide(MO) and in the other case chemically prepared (CP). The applicant used, the mixed oxide process to prepare the PLZTs. The mixed oxide (MO) is prepared by wet mixing the oxide powers of Lead (PbO). lanthanum (La2O3), Zirconium (ZrO2) and Titanium (TiO2). The mixture is then dried, calcined (a high temperature solid state chemical reaction), then milled to reduce the particle size to a desired level. A slug is then created by cold pressing, and then a wafer can be formed from the slug by hot pressing. The wafer thus produced is then sliced and polished for use as the panels for the liquid display. The wafer can be up to 15 cm in diameter and from 0.5 mm up to several millimeters in thickness after polishing. It consists of a uniform microstructure of controlled grain size of approximately 2 to 15 um. The grain size is important, as it places a lower limit on how close the controlling electric fields can be and thus limits the pixel size.
While Lanthanum Oxide is preferred, it should be noted that this invention is not necessarily limited to Lanthanum Oxide. Rather Lanthanum Oxide can be replace with other oxides in the PERIODIC TABLE of ELEMENTS, within the "LANTHANIDE Series". This includes Cerium Ce, Praseodymium Pr, Neodymium Nd, Promethium Pm, Samarium Sm, Europium Eu, Gadolinium Gd, Terbium Tb, Dysprosium Dy, Holmium Ho, thulium tm, Ytterbium Yb, Lutetium Lu.